This invention relates generally to machines for forming, filling and sealing packages from an elongated thin flat strip of flexible packaging material, the strip of material being first formed to a depending upwardly open tubular configuration, sealed longitudinally at overlapped vertically extending edge portions, sealed transversely along horizontal lines spaced vertically along the tube, and filled from above with measured quantities of product between successive transverse or end sealing operations. More particularly, the invention relates to an improved end sealing and stripping means in a machine of the type mentioned.
U.S. Pat. No. 3,027,695 entitled Method and Apparatus for Packaging, granted Apr. 3, 1962, illustrates and describes end sealing and stripping apparatus in a form, fill and seal packaging machine of the type which employs a movable tube former. That is, packaging material passes through a tube former adapted for vertical movement and which operates to move upwardly with end sealing jaws engaged with and securing a depending tube of packaging material against upward movement. The tube of packaging material beneath the former is thus elongated with the material passing through the former during its upward movement, a measured quantity of product is dispensed through the former into the tube, the former is then moved downwardly with the tube depending therefrom in a filled condition, and the end sealing jaws are engaged with the tube above the product with stripper means mounted on the jaws. A subsequent short upward movement of the former results in a "stripping" operation wherein the tube is cleared internally and flattened prior to full engagement of the sealing jaws and the completion of the end sealing operation and package formation.
The apparatus described is well suited to the movable tube former type packaging machine but is unsuited to the type of form, fill and seal packaging machine which employs a stationary tube former with independent tube feeding means therebeneath for drawing the strip of packaging material through the former and for thus forming the necessary depending tube of packaging material. Further, with the tube of material in tension between end sealing jaws and a movable tube former, the portion of the tube immediately above the jaws may be drawn into a relatively sharp or tight "V" configuration and such configuration is not conducive to an efficient filling operation, nor is the resulting stress on the tube of packaging materials at the end sealing jaws conducive to good end sealing operation. A packaging machine with independent tube feeding means such as the vacuum-friction belts of U.S. Pat. No. 4,136,505 entitled Tubeless Vertical Form, Fill and Seal Packaging Machine with Improved Feed Means, Jan. 30, 1979, avoids tensioning the packaging material between the former and the end sealing jaws and this is conducive to an efficient product dispensing or filling operation.
From the foregoing it will be apparent that an efficient stripping and end sealing operation should include a squeezing or flattening operation on the tube across an area above the end sealing zone and a smooth downward progression of the flattening operation to the end sealing zone resulting in clearing of the interior of the tube of product or product particles such as potato chips, and the preliminary flattening of the tube for efficient end sealing on full closing of the end sealing jaws. It is a general object of the present invention to provide such a stripping operation in combination with a highly efficient end sealing operation in the type of form, fill and seal package machine which employes an independent feed means such as a vacuum-friction belt and which avoids tensioning of the tube of packaging material between the tube former and the end sealing jaws.